The present invention is concerned with an improved process for refining phospholipid-containing vegetable oils which employs treatment with activated carbon during the preliminary stages.
More particularly, the present invention is concerned with an improved refining process for edible phospholipid-containing vegetable oils, especially soya oil, which comprises the steps of degumming the crude vegetable oil, passing the degummed oil through a bed of activated carbon, and finally subjecting the treated vegetable oil to vacuum steam stripping and deodorization.
The vegetable oils to which the present invention is applicable are those having a phospholipid level of 0.05% by weight and above. Phospholipids, or phosphatides, are lipoid substances that occur in cellular structures and contain esters of phosphoric acid. The aminophosphatides, or lecithins, which are mixed esters of glycerol and choline with fatty acids and phosphoric acid, are especially common. For example, the phospholipid content of crude soybean oil ranges from 1.1 to 3.2% by weight, and averages 1.8%, while the phospholipid content of peanut oil ranges from 0.3 to 0.4% by weight.
Thus, the improved refining process of the present invention is applicable to such edible vegetable oils as soya or soybean oil, corn oil, cottonseed oil, peanut oil, sesame seed oil and rapeseed oil, among others. On the other hand, the refining process of the present invention is not applicable to such oils as olive oil, palm oil, palm kernel oil, coconut oil, and babassu oil, among others.
The process of the present invention has proven especially suitable to refining of soybean oil, and it is, therefore, particularly applicable thereto. Soybean oil is, moreover, the most important vegetable oil produced in the United States, comprising about 82% of the present total annual vegetable oil production.. Thus, production of soybean oil in the United States is an important and extensive industry, with current annual production of edible soya oil being approximately 9.5 billion pounds. While crude soybean oil is stable and nonreverting in nature, it has a dark color and a strong odor and taste which make it regarded as unpalatable in that state. Consequently, a number of techniques have been employed previously in the art to refine the crude soybean oil. The resulting product, while initially a light colored oil with a bland and agreeable flavor, in many cases unfortunately reverts by stages to more unpleasantly flavored forms after standing for a short period of time.